{"id":"F2006B06761","name":"AD/SA-TP/13 - Brake Unit P/N AH51417 in Lieu of P/N AH50743","slug":"ad-sa-tp-13-brake-unit-p-n-ah51417-in-lieu-of-p-n-ah50743","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114593,"registerId":"commonwealth-F2006B06761-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SA-TP/13 - Brake Unit P/N AH51417 in Lieu of P/N AH50743","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  British Aerospace (Scottish Aviation) Twin Pioneer Series Aeroplanes\n\n \n\nAD/SA-TP/13 Brake Unit P/N AH51417 in Lieu of P/N AH50743 NK\n\nApplicability: All models.\n\n \n\nDocument: Scottish Aviation Mod. No. C729. Compliance: Forthwith.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused on one specific part replacement for one aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Extremely short document (under 150 words)","No defined terms section — uses only standard aviation abbreviations (P/N for Part Number)","Single, unambiguous requirement with no exceptions or conditional logic","No cross-references to other legislation beyond the parent Civil Aviation Regulations 1998","Clear applicability statement ('All models') with no carve-outs or exemptions","Simple two-part structure: applicability + compliance requirement"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to all models of the **British Aerospace (Scottish Aviation) Twin Pioneer** aircraft.\n\n**What it does:**\n- Requires operators to replace a specific brake unit part (Part Number AH50743) with a different, approved brake unit (Part Number AH51417).\n- This change is based on **Scottish Aviation Modification No. C729** — essentially a manufacturer-approved design change.\n\n**Who it affects:**\n- Owners and operators of Twin Pioneer aircraft (a vintage twin-engine transport plane originally built in Scotland).\n- Maintenance organisations servicing these aircraft.\n\n**Why it matters:**\n- Brake failures on aircraft can be catastrophic. This directive likely addresses a safety defect or reliability issue with the original brake unit.\n- The word \"Forthwith\" means **immediate compliance** — operators must make this change as soon as possible, not at the next scheduled maintenance.\n\n**Key point:** This is a **retroactive safety fix** — it applies to existing aircraft, not just new ones, and compliance is mandatory under civil aviation law."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"The directive replaces the previously used brake unit part number AH50743 with part number AH51417 for all Twin Pioneer models, thereby changing the approved installed brake-unit specification. This change is effected by the AD title and implemented through Scottish Aviation Mod. No. C729 with compliance required \"forthwith.\" (AD title; Document: Scottish Aviation Mod. No. C729; Compliance: Forthwith.)"},"complexity_factors":["Narrow technical scope: single component replacement (brake unit) specified by part numbers (AD title).","Clear applicability: applies to all Twin Pioneer models (Applicability: All models).","Single referenced technical document for installation: Scottish Aviation Mod. No. C729 (Document: Scottish Aviation Mod. No. C729).","Immediate compliance requirement: \"Forthwith\" creates a short implementation timeline (Compliance: Forthwith).","Part-number specificity: replaces one P/N with another rather than setting a performance specification (AD title).","Regulatory source is a standard airworthiness directive under Part 39/CASA (header), not a multipart legislative scheme."],"plain_english_summary":"This Airworthiness Directive requires immediate replacement of brake unit P/N AH50743 with P/N AH51417 on all British Aerospace (Scottish Aviation) Twin Pioneer aircraft, using Scottish Aviation Modification No. C729 for fitment. Operators, owners and maintainers must carry out and pay for the work forthwith; the Civil Aviation Safety Authority enforces the AD and any approval for alternative parts or methods must be sought from the regulator outside the AD."}},"importantCases":[],"_links":{"self":"/api/acts/ad-sa-tp-13-brake-unit-p-n-ah51417-in-lieu-of-p-n-ah50743","history":"/api/acts/ad-sa-tp-13-brake-unit-p-n-ah51417-in-lieu-of-p-n-ah50743/history","analysis":"/api/acts/ad-sa-tp-13-brake-unit-p-n-ah51417-in-lieu-of-p-n-ah50743/analysis","conflicts":"/api/acts/ad-sa-tp-13-brake-unit-p-n-ah51417-in-lieu-of-p-n-ah50743/conflicts","importantCases":"/api/acts/ad-sa-tp-13-brake-unit-p-n-ah51417-in-lieu-of-p-n-ah50743/important-cases","documents":"/api/acts/ad-sa-tp-13-brake-unit-p-n-ah51417-in-lieu-of-p-n-ah50743/documents"}}